Platinum-free fuel cell promises cheap, green power

作者：门匍舷 | 日期：2017-10-24 06:12:30

By Colin Barras (Image: dbking http://flickr.com/photos/bootbearwdc/2213871048/) Doing away with the use of the precious metal platinum could lead to a new class of low-cost fuel cells, Chinese engineers claim. Fuel cells produce water and electricity from hydrogen and oxygen, and have been invested in by car makers as a potential alternative to the internal combustion engine. But they have yet to be widely adopted, in part because the expensive metal platinum is a key component of the design. In a standard fuel cell, a platinum catalyst at one electrode breaks down hydrogen into protons and electrons. The protons pass through a proton exchange membrane to a second electrode where they react with oxygen to produce water. The electrons are syphoned off as electric current. Platinum has so far been the metal of choice because the membranes used in fuel cells create a very acidic environment, and the metal is stable in such corrosive conditions. Now, though, Lin Zhuang’s team at Wuhan University in Hubei province, China, has designed a new membrane that is alkali, not acidic – making it possible to use a much cheaper, nickel, catalyst. The team’s new polymer proves easy to make into fuel-cell membranes, and can also be mixed with the catalyst itself – this increases the contact between the two components and boosts efficiency. Previous attempts to change the acidic conditions inside fuel cells involved using liquids, not solids, says Zhang, but they risked forming carbonate deposits that can clog up the cell. “There has hitherto been no commercial alkaline polymer electrolyte suitable for fuel-cell use,” he says. Many are not stable at temperatures higher than 40 °C, but most fuel cells require more extreme operational temperatures, he says. A working prototype of the new low-cost fuel cell shows a “decent” performance of 50 milliwatts per square centimetre at 60 °C. “The power output is still lower than that of fuel cells using platinum, but such a comparison may not be appropriate because platinum fuel cells have been studied and optimised for decades,” Zhuang says. Allen Bard, a fuel-cell researcher at the University of Texas in Austin, told New Scientist that the new membrane is an interesting idea. He wonders, though, if it really will be free from carbonate clogging. “It may be less of a problem with an alkaline membrane, but it remains to be seen,” he says. Bard’s own research team is trying to develop platinum-free catalysts without changing the conventional acidic membranes. Palladium-based catalysts have proved almost as effective as platinum ones, says Bard. But, although cheaper than platinum, palladium is still a precious metal. Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0810041106) More on these topics: